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THE 




CEREBELLAR CORTEX. 



BY 

0. E. BEEVOR, M.D., Lond., MR.C.P., 

ASSISTANT rilYSICIAN TO THE NATIONAL, HOSPITAL EOR 
PARALYSED AND EPILEPTIC, LONDON. 



iUEPlllNTEJ) FROM ^BRAIN,' Pari XXllI.'] 



LONDON: 

PRINTED BY WILLIAM CLOWES AND SONS, Limited, 
STAMFORD STREET AND CHARING CROSS. 

1883. 




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\ BY 

C. E. BEEVOR, M.D., Loxd., M.R.C.P., 

ASSISTANT PHYSICIAN TO THE NATIONAL HOSPITAL POE 
' PARALYSED AND ElILEPTIC, LONDON. 



[UEPIUNTED FROM *BRAIN; Fart XZil/.] 



LONDON: 

PIHNTED BY WILLIAM CLOWES AND SONS, Limited, 

STAMFORD STREET AND CHARING CROSS. 

1883. 



LONDON' : 

PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, 
STAMFOUD 6TKEET AND ClIARIN-a CKOSS. 



THE CEEEBELLAR CORTEX.* 



BY C. E. BEEVOK, M.D. BOND., M.R.C.P. 

Assistant riiysician to the National Hospital for Paralysed and Epileptic, London. 

Dr. Gaule, under whom I liave worked, and whom I have much 
to thank for liis kind assistance, advised me to iise Wei^ert’s saure 
fuchsia method (Centrhl. fur die med. ITm. 1882, p. 753), wliich 
has produced excellent results. The first sections weie made 
from pieces of cerebellum, one centim. square, hardened in three 
per cent, soluiion of bichromate of potash and kept in a hot 
chamber at 35° C. for 4-8 days. They were then washed in 
water half an hour, then ])laced in alcohol 24 liours, and then 
for 24-28 hours in a concentrated aqueous solution of siiuie 
fuchsin, also at a temperature of 35° C. The pieces were then 
slightly washed in water and put into .strong alcohol and dehy- 
drated, imbedded in paraffin and cut into section.s, which were 
then fixed to object slides, the paraffin dissolved (mt,'-* and the 
sections washed out according to Weigert’s method with water 
and alkaline alcohol. 

In the second series of preparations they were further stained 
with nigrosine after the above treatment ; and these preparations 
proved the best. The third series were hardened in the same way, 
but after fixing the sections on the slides, they were stained by 
hajmatoxylin and eocene. This latter method of double staining 
has alread}' been employed by Denissenko. In the fourth method 
employed, the pieces of cerebellum were hardened by % chiomic 
acid, imbedded unstained, and the sections fixed on the object 
slide. The specimens were taken from the cerebellum of man 
(adult and new-born) dog, rat, rabbit, hen and pigeon. My des- 
cription is chiefly concerned with the dog, in which all the elements 
are most clearly shown. The human cerebellar cortex is the most 
developed, and as it is much richer in medullated fibres, and the 
inedullated sheaths are better developed, it would undoubtedly 
give better preparations, but unfortunately it is impossible to harden 
the pieces directly after death and so obviate post-mortem changes. 
And great stress is laid on the fact that in the preparations used 
for this paper, in less ihan an hour after death, the pieces were 
in the hardening fiuid in the warm chamber, which was used to 
introduce a quicker diffusion in the substance of the piece. 

’ This article is an extract from a paper published in the ‘ Archiv fiir Anatomie 
und Physiologie’ (Physiologische Abtheilung) and from work done in Professor 
Ludwig’s Physiological Institute in Leipzig. 

* Canini, in these Archive, 188R, p. 155. 

B 2 



( 1 ) 



1. — Granule Layer. 

Biifsis of desci'iplion, stinro fuchsin and nigrosine preparations. 
In these the medullated fibres are seen, as described in Fig. 1 and 
2 a, as a black or grej'- thread enclosed in the medullary sheath 
stained red. It is very important to note that the axis cylinder is 
dark and the medullated sheath red. If the saure fuchsin be not 
sufficiently washed out, other fibres which are not medullated are 
dyed red, but these have not the dark, central fibre which can be 
stained by nigrosine or haematoxylin, and my description refers 
only to these fibres. 

Fig. 1 is a longitudinal section of a lobule of the cerebellar cortex 
seen under a low power. Along the centre of this run the medul- 
lated fibres, radiating out and passing through the granule layer 
in the direction of the Purkinje cells. These fibres have been 
described by Deiters,^ who maintained the connection of the 
axis cylinder process of these cells with a medullated fibre. 
Koschewnikofif'^ has isolated Purkinje’s cells in connection with a 
medullated fibre. Hadlich^ says that from the white medullated- 
fibre centre, fibres proceed to the gi’ey red granule layer, divide, and 
pass as a priueipal nerve process into the lai-ge ganglion cell, into 
every cell one fibre. Golgi ^ makes the axis cylitider process, 
in its course thiough the granule layer, give otf branches at right 
angles. Other descriptions are of a similar nature. But how very 
indistinctly the fibres have been seen is shown by the very con- 
tradictory statements, as for instance some say : that the axis- 
cylinder runs direct to the medullary centre; that it runs in 
a horizontal direction ; that this axis-cylinder soon gets a medul- 
lated sheath, or that this occurs at a great distance from the cell; 
and that the fibre is fine, — or thick. Nearly all maintain that it 
divides. lladlich, and, later, Denissenko make reservations on 
account of possible deceptions. Hadlich’s statements seem to me 
the most correct. 

Fig. 1 shows a clear pictm’e of the whole arrangement of the 
nerve-fibres ; in each lobule some of them can be traced uninter- 
ruptedly in their whole course to the immediate vicinity of the 
Purkinje cells. The fibres leave the medullary centre with the 
slightest change of direction. At the summit of the lobule they 
radiate out like the out>tretched fingers of the hand. At the 
lateral part of the lobule they ascend slantingly in a slight curve 
through tlie granule layer, fi’hey run at definite distances from 
each other, corresponding to the distances between the Purkinje 
cells, to which their number, as far as can be ascertained, cor- 
responds. At the bottom of the sulci the fibres are closely 
aggregated and several pass through the gianule layer together. 

' Deiters, ‘ Untersuclnuigen iiber Celiiru imd RUckeiimark.’ Herausgegebene 
V. M. Sclmltze. 18(58. 

* Koschewnikoff, ‘‘ Axencylinderfortsatz der Nerveuzellen iui Kleiuliirn dea 
Kalhes;’’ M. Solmltze’s ‘ Ardiiv,’ 1869, Bd. v. 

^ Hadlicl), “ Mittheilung iiber 'den Bau der menschliclieii Kleinhiruriude.” 
Arcli. fiir luikr. Anat.,’ 1869, Bd. vi. 

* Golgi, ‘ Centialbl. fiir die mod. Wiss.’ 1879. 



( 5 ) 

Tlicpe fibres make a bend at Ihe border of the molecular layer, 
lunning parallel with it for a short distance ^seo 1} j they do 
not cross each other and do not branch ; but keeping the same 
thickness, they run stiaight through the granule layer with 
some slight wavings in their course. Their axis-cylinder is 
thick, the medullated sheath slightly varicose, often presenting a 
jointed appearance. In short, these fibres have in the granule 
layer the same formation they had in the medullary centre. Each 
remains an isolated medullated fibre w’hich, unbranched and in- 
dependently, directs its w-ay towards a particular ganglion cell. 
One can hardly doubt that tliese are their nerve fibres. Sections 
are not very adapted to trace the passage of a fibre into a structure 
of so much greater size. If the sections are very thin, the chances 
of finding the right spot are extremely small, and this difficulty is 
increased as the fibres always change their direction befiire enter- 
ing the cell. Isolated preparations show more easily the connec- 
tion, but then it is not certain that the fibres are of iho same 
nature. I have therefore not been satisfied till I could confirm also 
in section preparations the connection of the Purkiuje colls with 
one of these fibres. 

It can therefore now be said for certain that every Purkinje 
ganglion cell is in connection with a distinct, isolated, medullated 
nerve fibre. Besides the above described fibres, there are others, 
which have already been seen and which caused the different 
opinions concerning the fibres going to the ganglion cells, as it was 
not known that there were two different kinds of fibres. Only 
Hadlich ^ has as yet expressed this idea, and laid stress on the fact 
that the many divisions described must refer to fibres of the second 
kind. The second form of fibre produces a plexus which traverses 
the gramde layer in all directions, passing into the medul- 
lary centre on one side, and into the molecular layer on the other, 
'fhese fibres branch about and anastomose, they arc of different 
thickness, from the finest calibre up to that of the first kind of fibres, 
their medullated sheath is less developed, is always varicose, often 
interrupted, and sometimes the fuchsine reaction entirely fails. In 
man these fibres ajipear far more numerous and better developed 
than in the dog, when stained by saure fuchsin. Perhaps age 
makes some difference. 

It is quite clear that these fibres differ from those of the first 
kind. The latter pass through them without being connected 
vith them. Probably all branched fibres belong to the same 
species and have the same function. I shall designate the direct 
fibres of the first kind, joining ganglion cells as strairjht, or unhranched 
fibres, those of the second kind as branched or anastomosing fibi es. 

The spaces between the fibres in the granule layer are filled up 
by the closely packed cells. Formerly these cells were all called 
granules, and their cellular nature was doubted. Denissenko has 
shown that we have here two kinds of cells, one stained by haema- 
toxylin, the other by eocene. The haaniatoxylin cells correspond 



' Hadlich, op. cit. p. 20. 






( C ) 

to those formerly called granules, but they possess a miclens and 
protoplasm, and therefore tlie attributes of a cell. Denissenko 
regards these as connective tissue cells, whereas the eocene cells 
are connected with nerve-fibres.^ The reason why this formation 
was not recognised before, was because the cells are so tightly 
packed. Very thin sections have to be stained by a dye which 
will colour the protoplasm, for this is always present in the 
form of a very small layer around a relatively large nucleus. The 
protoplasm has numerous processes, very fine or thicker threads, 
which form a thick network with the threads of other cells. 

The threads refract light strongly and have a sharp contour, 
the meshes are fine. They are best seen, where the cells lie less 
packed together, at the borders of the granule-layer. Towards the 
medullary centre there is no sharply-defined boundary, and 
as in the granule layer there are everywhere fibres, so in the 
medullary centre there are similar cells scattered everywhere. 
But here the protoplasm is more abundant, the threads thicker, 
and the meshes of the network are very much larger and join with 
the narrow network inside the granule layer, re>embling the fine 
framework in the white substance of the spinal cord. The nucleus 
of these cells is very large and characteiistic. It possesses a dis- 
tinct thread-like appearance, with the above-meTi tinned method of 
hardening. The threads lie grouped in all kinds of forms in a 
round clear space. If these nuclei were richer in colouring matter, 
and if characteristic stages could be found, the idea of nucleus- 
division might be entertained. Some of the nuclei are certainly 
larger and their contour more distinct. The mass which is 
coloured by hacmatoxylin is naturally that of the nucleus threads, 
while the protoplasm, even when coloured by nigrosine, only 
appears as a narrow line running round the nuclear spot. Between 
the cells the medullated fibres make their way, and their medul- 
lated sheath comes into most intimate contact with them. The 
cell threads often seem to penetrate between the separate particles 
of the medullated sheath. Denissenko describes these cells as 
grouped round openings from which chmnels proceed, whose 
walls are likewise lined by these cells. This appearance is seen 
w'hen the cells lie particularly clos-e together. These channels are 
only the medullated fibres which have penetiated between the 
cells, whilst the place where the fibres cross each other gives rise 
to the apparent openings. If the cells are less closely arranged, 
the spaces occupied by these fibres are less compressed, and this 
presents the appearance of cells in groups surrounded by fibres. 

In these spaces other struefures are seen, which colour with 
eocene and nigrosine, and called by Denissenko, eocene cells. They 
seem to be interposed in the course of the medullated fibres, which 
cress over the cells. They are often really interposed, as can be 
seen by using nigrosine and saure fuch^in, when the cells 
become the same colour as the axis cylinder which is then seen 

* Henle and Merkel have already compured the granules to ihe cells of reticu- 
lated connective tissue, and have tlierefore described them correctly according to 
their appearance. 



( 7 ) 

to be in connection with them, while the inedullated sheath is 
interrupted. 

'PJieir cellular character is doubtful, as I can find no nucleus 
in most of them. The larger ones reiemblo multipolar ganglion 
cells by their form and size, as also by their connection with 
nerve fibres ; and as it is often difficult to discover a nucleus in 
ganglion cells when the protoplasm is colourerl, these are probably 
ganglion cells. The smaller of these cells are often deficient in any 
cellular character and appear to be thickenings along the axis 
cylinder. 

I think I can with certainty explain the use of the limmatoxylin 
cells, viz. that of glia-cells. These have not only nuclei, but are 
cells with protoplasm and processes; the processes form a network 
which extends through the whole granule layer, and which is 
also connected with a similar network in the medullary centre. 

These appearances are just the ciiteiion of glia-cells, and if one 
accepts glia-cells at all, they must bo cells like those above 
described. Schwalbe has lately objected to the glia-cells generally, 
from the hypothesis that the cells can be separated from the fibres 
of the finest network. But these objections are mostly theoretical. 
Besides, in my preparations, the network of the fibres proceeds 
from the body of the cell (see plate Fig. 2, h) and this agrees with 
what Henle and Merkel give in their work on the supporting 
structure of the central nervous system. Also in the description 
of the supporting framework of the molecular layer I have only 
to confirm their observations, agreeing with them that these 
cells are glia-cells, but doubting that they are cells of reticulative 
connective tissue, or that they may become ganglion cells. Since 
the embryologists have shown that the central nervous system 
proceeds from the ectoderm, and that there exists a thorough 
separation between the epithelial and connective tissue structures, 
the “ archiblastic and parablastic ” formations, it is probable from 
embryological researches, and what we know of its chemical 
nature, that the glia is an epithelial formation. 

The glia stands in relation to the ganglion cells and their 
protoplasmic processes, as the inedullated sheath does to the axis 
cylinder of the peripheral fibres. It is a continuation of this latter-, 
and there are forms of transition. The cellular elements are 
common to both ; from this can be explained, what might be con- 
sidered an objection to the definition of these granule cells as 
glia-cells, viz., their accumulation into distinct regular layers. 
Where numerous fibres lose their medullated sheath (those of the 
first type), or acquire it (those of the second typo,) there are to be 
lound accumulated the cellular elements which are common to the 
glia and the medullated sheath, and where this occurs in regular- 
planes in the cerebellum, the position of the cells is found to 
correspond. 

2. — Molecui.ar Layer. 

a. The ground Substance . — This layer owes its name to the 
peculiar substance forming its foundation. The older authors 



I 



( 8 ) 

describe it as a finely granulated mass, in wliich a finer structure 
is not recognisable; however Fromman has already shown it to 
be a sponge substance built out of a network of threads. Kiihne 
and Ewald haA’’e proved that we have here a formation of a 
peculiar chemical structure, analogous to the horny framework 
of the medullated sheath of the peripheral nerves. Schwalbe 
describes the suV>stance in his ‘Lehrbuch der Neurologic’ as a 
fine network, the fine trabeculee being composed of neuro-keratin e. 
This opinion is also borne out by my plates, Fig. 2, b-d. The clear 
substance lying in the enclosed spaces of this network becomes, 
with the means used to clear up the medullated substance, as 
clear as this latter ; the osmic-acid luethod cannot be applied, as 
the distinction between the trabeculje and its meshes only comes 
into view with very thin sections, and these can only be made 
after treatment with alcohol. The saure fuchsin method, however, 
produces a very characteristic action on erythrophile substances. 
In many of the mesh-spaces, but not in all, a fine red line bounds 
the clear contents, in the same w^ay as seen in the cross-section 
of nerve-fibres. 

These red-bounded spaces are larger or smaller in size, and some- 
times several in a row. But they are not sections of fibres, as can be 
seen from the absence of any axis c}dinder ; neither are there, 
where they lie, so many fibres visible, which is easily proved by 
alteiing the direction of the section. It thus becomes probable 
that as this network corresponds to the horny framework of the 
medullated sheath, so also this intermediate substance corresponds 
to the myelin ; but not chemically, for even the medulla substance 
of the periphery differs fi om that of the central nervous system in 
not re-acting to saui’e fuchsin ; and we must consider that the relation 
of the neuroglia of the central nervous system diflfers more from 
the peripheral nerves than does the medulla of the fibres of the 
central nervous system. There are, however, many transitions, viz., 
the above described varicose sheaths of the brancihed fibres, which 
often form separate round formations and the glia- nets containing 
erythrophile substance. Another analogy becomes visible, when 
we consider the cellular elements of both, viz., the glia and the 
medullated sheath. Eanvier has acquainted us with the cells of 
the medullated sheath, and he concludes that the myelin is enclosed 
in the meshes of their protoplasm. Tow'ards the sheath of 
Schwann and the axis-cylinder the protoplasm is thickened to form 
the inner and outer protoplasmic sheath. When this theory was 
proposed, Kiihne and Ewald had not yet discovered their horny 
sheath, which probably corresponds to Kanvier’s protoplasmic 
sheath, if neuro-keratine be substituted for pn>toplasm. I think 
it probable that from the protoplasm of the yimng cell, neuro- 
keratine is formed by differentiation, as is similarly described by 
Waldeyer in the horny change of the epideimis cells. There, a 
stroma of keratine threads foims itself out of the protoplasm of the 
cell, while in its meshes, a fatty substance, eleidin, is deposited. 
It is difficult to distinguish between the sheath and the framework. 
Either can resolved into neuro-keratine. Probably transitions 



( 9 ) 

between the two will be found. I have also tried to convince 
my.self in preparations of the horny sheath, treated by Kuhne’s 
method and coloured by baematoxylin and nigrosine, whether the 
neuro-keratine threads really are in connection with the nuclei of 
the medullated sheaths, and I can assert that one can really see 
this, so far as it can be observed. Assuming the horny framework 
of the peripheral nervous system to be a formation of cells, its 
relation to that of the central nervous system appears all the more 
assured. For not only the network of the granule layer already 
desci ibed, but also the network of the molecular layer, appears as 
glia-cells. The connection between both is best observed in the 
collection of glia-cells to be found at the base of the molecular 
layer. \\ hen from any reason, the molecular and granule laye’S 
are separated — which may be caused even by pressure of the 
cover-glass — there remains one or more layers of cells separated 
with the molecular layer. The separation occurs below the 
Pnikinje cells, where the unbranched fibres bend round and 
spread out. Here, the layer of glia-cells attached to the mulecnJar 
layer forms a membrane, by joining their processes, to support both 
the fibres and blood-vessels spread out under it, and the Purkinje 
cells resting on it, and to form also the groundwork of the 
molecular substance. In Fig. 2 fc, this is shown in section. Ils 
cells are generally larger than those of the granule layer, as are 
also their protoplasm and processes, which here become very 
distinct. Many are pyramidal or pear-shaped, with their broader 
basis turned to the granule layer, and form, with the long processes 
given otf from the glia-nets of the granule layer, that mem- 
brane of the molecular layer which may be represented as a 
fiat network broken up by the cells interspersed in its ineslies. 
Through this membrane pass all the numerous fornialions on their 
way from the granule to the molecular layer, and vice vensa. As 
the name of limitana externa has been adopted by Henle and Mei-kcl 
for the layer of the glia-nets which is in contact with the pia mater, 
and this layer, by its formation and origin being completely 
analogous to the above-mentioned membrane on the inner surface 
of the molecular layer, I propose to call the latter limitana interna. 
Some of the processes from its cells, which are vertical to tlje 
limitans interna and go off from the apex of the cells, are parti- 
cularly thick and can be traced far into the glia-network; and at 
regular intervals these processes are still thicker and reach to the 
limitans externa, to which they are attached by a flattened pedicle 
and serve as supporting pillars to the molecular layei-. These 
were discovered by Bergmann and described by Ilenle and Merkel. 
They have also described the limitans externa as a special mem- 
brane, separable from the pia mater, and consisting of glia threads. 
Obersteiner has described one or two c 11 layers under the pia 
mater in the new-born animal, from which layers is developed the 
limitans externa, as well as the supporting pillars; probably the 
limitans externa has the same character in the new-born as the 
Innitans interna in the adult, so tliat the pedicles are remains of 
pyramidal cells, whose apex processes formed supporting pillars 



( 10 ) 

ami basal processes the network of the liinitans externa. 'J’ho 
network between the membrane is also piobably the remains of 
the cells described by Obersteiner, as filling up the embryonal 
molecular layer, and which have been absorbed with the growth of 
the network ; as the network is too extended to have been formed 
from the supporting fibres, or from the glia-cells scattered in the 
molecular layer. Perhaps the protoplasm of the embryonal cells 
may have been converted info neuro-keratine. Two further points 
about the glia-cells remain to be discussed. (1) Their relation to 
the ganglion cells and their processes; (2) their relation to the 
connective tissue. 

(1) We have already mentioned that the glia-cells are accumu- 
lated round the ganglion cells (see Fig. 2 b). Whilst the ganglion 
cells at their lower part rest on the limitans interna, they are 
packed at the sides by these heaped up glia-cells, so that the cells, 
together with the limiting membrane, closely surround a hollow 
in which the ganglion cell lies. At the upper and lower part the 
processes pass out. This walling-in is seen best when the Purkinje 
cell has been detached from its space, which is then seen spun over 
with a network of fine fibres, which are continued at the sides into 
the bodies of the glia-cells. This capsule is thus formed by a net 
of neuro-keratine threads, supported by a denser accumulation of 
cells similar to that found in the limitans interna. A somewhat 
similar capsule has been described by Denissenko and by former 
authors. Of course such a capsule consisting of a network will 
allow the cell a free connection on all sides ; there is, however, 
a special condition for the axis cylinder and the protoplasmic 
processes. The former seems to acquire a continuation of this 
capsule as a sheath, which is connected with the medullated sheath 
of the nerve-fibre. But I have no definite drawings on this point. 
As is evident from Fig. 2, b, c, everywhere in the course of the 
protoplasmic processes- the glia-nets suriounding them ‘become 
thickened, so that numerous thieads seem to be attached to them, 
whilst on each side, the meshes of the glia-nets become larger. 
This attachment of glia-threads has been described by Hadlich 
and other authors, who state that the protoplasmic processes appear 
rougli, or that extremely fine threads go off from them laterally. 

This attachment is however only apparent ; it is in reality only 
a tube-like thickening of the network around these processes, 
forming a sheath of neuro-keratine threads, continuous with the 
capsule of the ganglion cells. This appeaiance resembles the axis- 
cylinder of the peripheral nerve fibre (when treated according to 
K-uhne’s method), which is closely surrounded by a thickening of 
the horny structure, decribed by Kiihne as the inner homy sheath, 
and here the keratine threads often seem to join the axis-cylinder 
itself. The broad meshes of the glia-nets on the sides of the 
protoplasm processes correspond to the space between the inner 
and outer horny sheaths, which is also traversed by a few threads. 
A formation analogous to the outer horny sheath is absent in the 
glia. The resemblance between the relation of the protoplasmic 
process to its glia, and the relation of the axis-c}’linder to its horny 



( 11 ) 

sheath helps very much the comprehension of the central nervous 
system. But the sheaths in the glia are not isolated, they are in 
connection everywhere, and are only interrupted by the branching 
out of the processes. In the glia, the homy component part is 
unduly in excess of the thread network, as compared with the fatty 
part enclosed in the meshes : and the fatty substance is not identi- 
cal with mjmlin of the peripheral nerves. As Weigert’s reaction 
is only sometimes shown, probably different gradations of myeline 
exist in the nerve-fibres of the periphery and in those of the central 
nervous system, where varicose fibres occur, increasing as they 
become finer. 

(2) It is not easy to establish the boundary between the glia and 
the connective tissue. When they were still unconditionally classed 
together, it was observed that there by no means existed an 
immediate connection between the pia and the glia lying under it. 
Ilenle and Merkel — who in their treatise assume that glia, nerve 
elements and connective tissue are produced out of the same materials 
— describe, however, that the glia limits itself by a lamina limitans 
externa, and that this is easily detached from the pia, being 
separated by spaces traversed by single threads, — subarachnoid 
lymph spaces. A retraction of the glia from the connective tissue 
sheaths of the vessels leads to the production of the peri-vascular 
spaces. The glia therefore is only in connection at single points 
with the connective tissue, which is necessary to give support to the 
whole framework. In short there seem to be connecting-fibres 
only between the pia and the limitans externa, as these fibres do not 
sink deeper into the glia-network. 

I'he connective tissue of the pia may be compared with the 
Schwann sheath of the peripheral nerves, if the glia be ounpared 
with the mednllated sheath ; and as between the Schwann primitive 
sheath, and the medullated sheath, so between the connective tissue 
and the glia, there exists only a loose connection ; from this it does not 
follow that the glia might not histologically bo reckoned with con- 
nective tissue. But this depends entirely on whether or no the glia- 
cells are descended from epithelium cells of the ectoderm, for our 
present classification of the tissue is essentially generic. From the 
above, it is no lonu.er possible to treat of the glia as an undefined 
boundary between nervous and connective tissue. We have then in 
the nervous system three distinct systems lying close together : 

1. Axis cylinders. Ganglion cells. Protoplasm processes. 

Medullated sheaths. Glia-cells. Glia net-works. 

3. Schwann’s sheath. Pia mater. Connective tissue-sheath. 

Of these systems the first only can be designated as nervous. 

h. The Nervous elements . — One link in the chain of this nervous 
system fails us. The branched processes of the Purkinje cells 
must enter again into connection with nerve fibres. It is easy 
to trace the branches to close to the limitans externa, but here 
every diiect trace is lost. Kindfleisch and Strieker suppose them 
to become lost in the ground-substance of the neuroglia, but 



( 32 ) 

tin’s has been very much contested, as it is against the physio- 
logical demand for a definite course. In my preparations I find no 
indication of a connection of the ganglion-cell processes with the 
threads of the glia network, A second view makes the pro- 
cesses end in peculiar nuclei, which lie at the periphery of the 
molecular layer. I have found it difficult to discover what form 
of cells Denissenko means by these peripheral nuclei, for at 
the limitans externa or towards the inner part of the periphery, 
there are very few cells to be found in the adult animal. Nu- 
merous cells are present in the young animal onlj*. Denissenko 
calls these cells nuclei, and yet states that they are very little 
coloured by nuclei staining fluids, and further, that in some animals, 
fibres spring from them which penetrate vertically the molecular 
layer. The latter fibres correspond to the supporting fibres of the 
glia, and I consider that the so-called peripheral nuclei are the 
pedicles with which the supporting fibres attach themselves to 
the limitans externa. The degree of coloration mentioned by 
Denissenko agrees also with these pedicles, which might also be 
called nuclei, as they are possibly the remains of cells; but with 
the processes of thePurkinje cells these pedicles are not connected. 

This view of Denissenko agrees with Golgi’s, avIio makes the 
processes of the ganglion cells end in connective ti.-sue corpuscles 
at the periphery, which Denissenko even conjectures to be partly 
identical with his peripheral nuclei. With the excei3tion of the 
sheaths of the vessels, I must decidedly dispute the presence of 
real connective tissue corpuscles at the periphery of the molecular 
substance on the inner side of the limitans externa. A third 
view makes the processes of the periphery bend round and run 
back to the granule layer ; and to prove this, certain fine straight 
fibres, which traverse the molecular layer vertically to the 
periphery, have been pointed out as these processes (Boll) ; but 
the greater number of these fibres can be traced to the limitans 
externa where they end in pedicles. They are the supporting fibres, 
as others have already showm. 

Lastly, Hadlich has suggested that the ganglion cell processes 
return again in the same form. This appears at first difficult to 
contradict, as the processes ma^^be either running out or returning. 
But Hadlich has already conjectured that there might be two kinds 
of nerve-fibres, one entering into connection with the axis cylitider 
of Purkinje’s cells, the other with the already mentioned returning 
branched processes. The latter therefore would not return to gan- 
glion cells, but join directly with nerve fibres. In this way we have 
a distinct criterion by which to recognise the out-going from the in- 
going fibres, and a proof of whether they really exist. I have looked 
through my preparations and found that there are numerous places 
where, in the deeper par ts of the molecular layer, all ganglion cell 
processes can be traced to their corresponding Pui kinje cells. 'J’his 
precludes the possibility that the protoplasmic processes, after 
spreading themselves out at the periphery, should collect together 
and return in the same form to the granule layer, to join with nerve- 
fibres. Another hypothesis assumes that the reluming processes 



( - 13 ) 

reassemble in the ganglion cells, of which there are two kinds, and 
which are not to bo distinguished in tbeir outward appearance. But 
this is contradicted by the fact that the branched mednllated fibres 
can be traced far into the molecular layer. The object of these 
fibres could not be seen, if the protoplasmic processes return to a 
o-anglion cell lying at the border of the granule layer before join- 
Tiig the neive fibres. Besides tliis the number of unbranched 
fibres is probably just as largo as that of the ganglion cells, so that 
we can drop the hypotho'is of two kinds of ganglion cells. If the 
number of the unbranched fibres is just as many as the Purkinje 
cells, and if they end at the granule layer, whilst the branched 
fibre’s extend into the molecular layer, the probability becomes very 
great that this cell is in connection with both kinds of fibres, with 
those in the granule layer by its axis cylinder process, with the 
others in the molecular by its branched protoplasmic processes. 

Fi<>-. 3 is drawn from a section cut parallel to the surface, and 
therefore at right angles to the direction of sections hitherto shown. 
1’he drawing represents the bottom of a sulcus, so that not only the 
molecular layer, but also the Purkinje cells and a portion of the 
granule layer are visible on each side. The medullated fibres 
appear on the flat surface of the section, running in two directions 
at right angles to each other, and round the Purkinje cells are 
numerous fibres passing into the molecular layer. The section here 
given is very thin, or else the fibres would be very numerous, as is 
the case in thick sections, where it is difficult to see individual fibres. 
This horizontal plexus is most dense in the deeper parts of tlie 
molecular layer, around and immediately above the Purkinje cells. 
But also in the more superficial planes, fibres running in the same 
direction can be seen, and the better the reaction has succeeded, 
the further does their region extend. They are all much finer than 
the unbranched fibres, but of the same calibre as the finer branched 
fibres. In the corresponding vertical sections of the lobule, fibres 
are seen in bundles close round the capsule of the Purkinje cells 
and passing into the molecular layer. Little of the above described 
horizontal plexus can be seen in these vertical sections, as the one 
set of fibres is cut across (compare Fig. 2, 6), while the other runs 
parallel to the surface. On the other hand there are fibres visible, 
Avhich descend vertically in the third plane. These are also fine 
and often run close to the supporting fibres. Generally these 
cannot be traced further than through half the molecular layer. 
Beyond that, although ei ythiophile substance is met with, it is not 
arranged in the form of fibre sheaths, but in isolated rings, without 
any connection. Probably these single rings must stand in some 
relation to the continuation of the system of medullated fibres. 

As the connection of the fibres of the molecular layer with the 
fibres of the second kind in the granule layer is very distinct, we 
may say that there exists here a fibre system, which, starting as a 
plexus from the medullary centre, branches through the granule 
layer, until the finest fibres are lost in the molecular layer, whilst 
their medullated substance can be traced further than the axis- 
cylinder. 



( n ) 



As regards the connection of tlie separate elements it is easy to 
establish the following points of a scheme : 

1. Each unhmnchecl fibre is connected with each Puricinje cell. The 
axis-cylinder passes into the protoplasm of the cell, the medullated sheath 
into the glia-like capsule of the cell. 

2. The axis-cylinder becomes converted into a number of fibrils in the 
cell, which pass into the branched protoplasmic process, the fibrils run 
in the process, ivhich is surrounded by a glia-sheath, as completely distinct 
threads as far as the periphery. In the branching of this process, the 
numerous fibrils, contained in it ichere it leaves the cell, are gradually 
distributed until they become isolated. 

My preparations show that the arrangement of the ganglion cells 
corresponds to M. Schultze’s scheme. Obersteiner has already 
described this for the Purkinje cells. Sometimes fibrils cross each 
other at the points where the processes branch. 

3. The fibrils thus isolated bend round at an angle of 90° (not 180°), 
spread themselves out in a plane lying parallel to the surface, and re- 
arranging themselves in definite order as fibres surrounded by a medullated 
sheath, run, with frequent interchange between the fibres, in the form of a 
plexus back to the medullary centre. 

This third point of the scheme contains, of course, much that is 
hypothetical. But there can be litile doubt that the fibres of the 
second system serve to establish somehow a connection with the 
branched processes of the ganglion cells. To explain why the 
fibres should not bend at an angle of 180°, instead of 90°, I must 
refer to Obersteiner’s discovery that the protoplasmic processes of 
the Purkinje cells only spread out in a plane at right angles to the 
surface, and also to the direction of the lobule and the plane of the 
medullated fibre laj^er. On the other hand, the medullated fibres 
of the molecular layer run in planes parallel to the surface, and at 
right angles to the planes of the processes. The processes only 
need now to bend round at an angle of 90° to pass into the plane 
of the fibres. Certainly other fibres are required which shall turn 
at an angle of 90° and connect the higher lying planes with the 
lower, but these fibres would be coarser and medullated. The 
strictly angular arrangement of the elements of the cerebellum is 
remarkable, both in the nervous elements and in the supporting 
structure. The important point is that we do not see the con- 
necting elements between the ends of the protoplasmic processes 
and the beginning of the nerve fibres ; and in the absence of any 
really decisive result, some other solution of the problem is possible. 
Perhaps future research will reveal that just at that point where 
the continuity of the elements is lost, an arrangement intervenes 
which we cannot now recognise. 

Further, there are medullated fibres under the pia mater Ij ing 
on thelimitans externa, broad fibres of a similar character to those 
of the medullary centre. 

The same fibres may be seen passing through the molecular layer 
in a slanting direction. A second collection of medullated fibres of 
the same character lies half-way up the molecular substance. 
Both imn parallel to the medullary centre. As those fibres are 



( 15 ) 



only found in a KUiall minority of the lobules, lliey are pr.-bably 
an aberration of the medullary centre. 

Sometimes the Purkinje cells of the same lobule differ in ap- 
pearance. Some show, as seen in Fig. 2 6, a distinct nucleus, 
with the nucleolar contents surrounded b}- a ring of nuclear 
substance, and in the protoplasm, a distinct fibrillous formation 
which completely fills up the glia-capsule and in the double- 
staining with nigrosine and saure fuchsin are stained a light grey 
colour by the foimer only. 

In the other kind a nucleus is hardly to be distinguished, and 
no fibril-formation ; the cell appears as a homogeneous body which 
remains dyed by same fuchsin, even after washing out by alkaline 
alcohol. The cells and their processes are slightly retracted from 
the glia, and the relation between the capsule and its sheath is not 
quite so distinct. It is not probable that there arc here two kinds 
of ganglion cells, as the difference in tlie cells is only seen in some 
of the lobules. It is hardly due either to different action of the 
hardening re-agent or to the fact of one cell dying before the other, 
as an external influence would act differently on the cells of two 
distant lobules, but not on those of the same lobule. We must 
conclude that the condition of cells must haVe originally been 
different at the moment of death. 



EXPLANATION OF THE PLATES. 

o Unbranchcd broad nerve-fibres of the first kind. 

a' Purldnje’s cells. 

a" Their protoplnsmic processes. 

o'" Branched fibres of the second kind. 

/3 Glia-cells of the granule layer (granules, glia-cells). 

Cells of the membraua limitaus interna. 

Supporting fibres (long radiating processes of the glia-cclls). 

0"' Glia network (short branched processes of the glia-cells). 

Membrana limitans externa. 

7 Pia Mater. 

5 Non-nucleated structures of the granule layer, stained by Eocene and Nigrosin 
(Eocene-cells). ° 

GENERAL "VIEW MAGNIFIED WITH A LOW POWER. 

Fig. 1. Longitudinal section of a lobule from the cerebellar cortex. Medullary 
centre— internal or granule layer — external or molecular layer. The pia mater 
with its blood-vessels is slightly separated. Shows the radiation of tl;e un- 
brancliecl fibres from tlie medullary -centre tlirough the gmiiule layer to tie 
Puikinje’s cells. 

Fig. 2. Details of the same section seen by a higher power U. oil immersion) 
show ing ; ^ 

a. Granule layer. 

h. Boundary between granule and molecular layers. 

c. liliddlo ot the molecular layer. 

d. Outer part of the molecular layer. 



( ) 

The figs. 2 a-d are to be taken in series. 

2. a, allows fibres of the first kind, a, and of the second kind a'" between 
the glia-cells, |8, and the eocene cells, 5. 

2 b. A Purkinje’s cell, a' with its protoplasmic process, a" which breaks 
up into fibrils. The glia-cells of the lamina interna, )3', some of them large 
and rich in protoplasm, are heaped around the Purkinje’s cell. The glia net- 
work )3"' proceeds from the processes of the glia-cells, some supporting fibres 
/3" are here not sien joining the cells. In the meshes of the glia-nets are seen 
sections of medulTated fibres of the second kind, a'", stained red. 

2 6‘. The glia-cells, in the interval between two Purkinje’s cells, form by their 
intimate connection the limitans interna, )3'. Some pyramidal-shaped glia-cells 
are elongated into processes which extend direct to the periphery and form 
supporting fibres j3". 

2 6*. A Pm-kinje’s cell in the glia capsule. The cell is seen, so as to show 
clearly its capsule. The threads of the glia are partly visible coursing over the 
cell. 

2 c. Glia network in the middle of the molecular layer. Very clear broad 
trabeculae of the network, /3"', which is traversed by parallel supporting-fibres 
i3", and also by a branching process from a Purkinje’s cell, showing fibrils, a". 

2 cb A supporting fibre, ;8", in connection with one of the solitary glia-cells 
found in this region. 

2 d. The periphery of the lobule, with the limitans externa )3'" cut across at 
right angles, and with the supporting fibres, /3", attached to it by broad pedicles ; 
between them is the glia network. 

Fig. 3. Horizontal section (parallel to the surface) through a lobule of the 
cerebellar cortex near the boundaiy between the molecular and granule layers, 
' which is depicted at the periphery of the drawing, so that the Purkinje’s cells 
appear surrounded by medullated fibres of the second kind which having reached 
the molecular layer, spread out in the plane of the section, in two directions at 
right angles to each other. 

These plates are faithful representations of the preparations, and are not in 
any way schematic. 



LONDON: I’lUNTED DY WILLIAM CLOWES A'D SONS, LIMITED, STAUt'ORD STKEKl 

AND CHARING CROSS. 



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